'Gay genes' have been in the news again this week. An Italian team of researchers has attempted to explain how such genes could be passed on from one generation to the next. The answer, it seems, is that the female relatives of gay men tend to have more children than those of heterosexual men. And any gene that increases the number of offspring of either sex has an advantage, in evolutionary terms. So, indirectly, the study supports the notion that homosexuality has a biological basis, something that many scientists and gay activists have long argued.
Sexuality, like all aspects of human behaviour, is the result of complex interactions between many different biological, environmental and cultural factors. But when Dean Hamer first reported his studies into the genetics of homosexuality eleven years ago, some scientists and the media leapt upon the work as evidence for 'the gay gene'. Some commentators expressed fears that the day was fast approaching when parents would be able to select offspring on the basis of their sexual preferences. This was despite the fact that no gene had been identified, just a possible location for one, on the human X chromosome.
Six years later, it emerged that another group of scientists had failed to replicate Hamer's findings and, in 2004, it is clear that there will be no single 'gay gene'. The author of the latest study, Andrea Camperio-Ciani, stresses that his work backs up the scientific consensus that several different genes influence sexuality - probably including one on the X-chromosome - but also that other factors are involved. These could include influences such as birth order, as well as life experiences. Camperio-Ciani estimates that his study accounts for just 20 per cent of the likelihood that a man will be homosexual, so being gay is clearly not all about genes.
Those who fear that we live in an increasingly 'geno-centric' society, with media coverage of human genetics dominated by simplistic explanations of 'the gene for...' variety, should have been pleasantly surprised by the coverage of this latest study. Although most reports were accompanied by images of homosexual pop star George Michael, nearly all did a good job of conveying the complexities of research in this area. In particular, Mark Henderson of the Times (see Recommends) gave a clear explanation of why such work will not lead to designer babies selected on the basis of sexuality, and concluded that 'variety is all part of normal human diversity'.
Like many multifactorial traits, research into human behaviour is technically challenging, but it also raises ethical issues that do not arise from other areas of genetic research. There are fears that such knowledge could theoretically be used to select for certain 'types' of people, a concern highlighted by a Nuffield Council on Bioethics report on the subject published two years ago. However, the more we find out about human genes and the way they interact with other factors, the less realistic these scenarios appear to be. It seems that the media, and therefore the public, might at last be getting the message that we are far more than the sum of our genes.